Thesis (Ph. D.)--University of Texas at Austin, 2001. / Vita. Includes bibliographical references. Available also from UMI/Dissertation Abstracts International.

Thesis (M. Communication Pathology)--University of Pretoria, 2003. / Summary in English and Afrikaans. Includes bibliographical references.

This report compares programmes of coordinated recipient control for rivers in northern Sweden. The aim was to investigate differences in the programme of the Ume and Vindel Rivers compared with those of Skellefte, Torne, Kalix and Ångerman Rivers. Future impacts on Ume and Vindel Rivers, and consequently the programme, were also studied. A quantitative method, namely meta-analysis, was used in order to collect data of programmes on Water Information System Sweden (VISS). The results of this study showed that the programme for the streams is slightly different regarding measured parameters, number of sampling points and sampling frequency. However, the similarities between the programmes of Ume and Vindel Rivers and Torne and Kalix Rivers are greater than compered to Skellefte River. The conclusion is that the differences in the programmes may have a natural explanation such as different emissions to the recipients, but can also indicate different ambitions. The programme may be affected and in need of change if a potential nickel sulphide mine in Tärnaby, Storuman is established and joins the water conservation association of the Ume and Vindel Rivers. Intensified forestry might also increase future impacts.

Previous studies have demonstrated that the magnitudes of otoacoustic emissions (OAEs) measured during behavioral tasks requiring attention were different from OAE magnitudes measured during tasks that did not require attention. The implication of these results is that the cognitive and perceptual demands of a task can affect the first neural stage of auditory processing—the sensory receptors themselves. However, the directions of the reported attentional effects have been inconsistent, the magnitudes of the observed differences always have been small, and comparisons across studies have been made difficult by significant procedural differences. In this study, we used a nonlinear version of the stimulus-frequency OAE (SFOAE), called the nSFOAE, to measure cochlear responses from human subjects while they simultaneously performed behavioral tasks requiring selective auditory attention (dichotic or diotic listening), or relative inattention. The results indicated statistically significant systematic differences in nSFOAE magnitudes within subjects, but opposite directions of effect across subjects. Differences in the nSFOAEs measured during the dichotic- and diotic-listening conditions suggested that cochlear responses differed in these two types of selective-listening tasks. Time constants measured from functions fitted to the nSFOAE responses indicated faster efferent effects during selective listening than during inattentive listening for the majority of subjects. Furthermore, measurements in brief silent intervals after the nSFOAE stimuli indicated weaker residual nSFOAE magnitudes during selective listening than during inattentive listening for every subject. This collection of findings supports the hypothesis that auditory attentional demands can modulate cochlear processing, presumably to the benefit of the listener. / text

Relative humidity (RH) is an important parameter associated with occupant comfort in buildings. However, the effects of RH on indoor source off-gassing and interactions between air pollutants and indoor materials are poorly understood. For this study, air samples were collected in residential buildings to characterize “background” concentrations of volatile organic compounds (VOCs) in air. The interior space was then humidified for several hours prior to collection of another air sample to characterize the effects of increased RH on VOC concentrations. Samples were analyzed by GC/FID with abundance “binning” by elution time. Some samples were also analyzed using GC/MS to identify specific VOCs. Results indicate that increasing RH is associated with increases in VOC concentrations in residential indoor air. Many of the chemicals that show enhanced off-gassing are associated with architectural coating, moth repellents, and cleaning agents. The results of this study are novel and may have implications with respect to health effects associated with damp buildings and increased respiratory effects of children during sleep in bedrooms with elevated RH. / text

published_or_final_version / abstract / toc / Speech and Hearing Sciences / Master / Master of Science in Audiology

A methodology was developed to dissect diesel particulate filters to study the time effect of loading for two different fuels: ULSD and a biodiesel blend. Filters loaded with soot from a diesel engine for exposure times of 1, 2, 5 and 10 hours were fractured and samples of filter substrates were analyzed using Raman spectroscopy and scanning electron microscopy. Observations revealed the sharp rise in pressure drop to be attributable to the clogging of the pores in the channel wall, leading to the formation of a pore-bridge. Cross sectional imaging of wall sections revealed this pore-bridge to be shallow, with significant particulate depositions limited to the first quarter of the depth of the filter walls. Images revealed increasingly dense deposits and the formation of coarse particles and soot cakes. Raman spectroscopy revealed no significant graphitization of the soot cake. The dissection methodology exhibits significant potential for future studies on DPFs.

A methodology was developed to dissect diesel particulate filters to study the time effect of loading for two different fuels: ULSD and a biodiesel blend. Filters loaded with soot from a diesel engine for exposure times of 1, 2, 5 and 10 hours were fractured and samples of filter substrates were analyzed using Raman spectroscopy and scanning electron microscopy. Observations revealed the sharp rise in pressure drop to be attributable to the clogging of the pores in the channel wall, leading to the formation of a pore-bridge. Cross sectional imaging of wall sections revealed this pore-bridge to be shallow, with significant particulate depositions limited to the first quarter of the depth of the filter walls. Images revealed increasingly dense deposits and the formation of coarse particles and soot cakes. Raman spectroscopy revealed no significant graphitization of the soot cake. The dissection methodology exhibits significant potential for future studies on DPFs.

This study investigates the relationship between three types of retail, Big Box, traditional and online retail, and their transportation related emissions. The study takes a comprehensive approach by examining both the consumer and freight emissions associated with each retail type. The retail environment has been evolving dramatically over the past 60 years, and this has many effects on an urban environment that are important for urban planners to understand. Although retail can influence the city in many different ways, this study isolates transportation. Using case studies in the Greater Toronto Area and the Transportation Tomorrow Survey, a scenario model is applied to compare the retail types. The key influences examined in the scenarios that alter consumer related emissions are return rate, the number of items bought, trips where no items are bought, trip chaining and browsing before buying online. The key influences on freight transportation are the not at home delivery scenario and the number of items delivered. The results show that as a base case, Big Box retail has the largest emissions, traditional retail the second largest and online retail the smallest emissions. Consumer transportation has a larger impact on the total emissions than freight transportation, which is the main reason Big Box retail has the largest emissions. However, the various scenarios examined demonstrate that the key influence can have a very large impact on the results, making it difficult to conclusively say Big Box retail has the largest emissions associated with it. Conclusions that can be drawn from this study for urban planners are that for physical retail, traditional style retail tends to have smaller emissions. As well, the key influences, in particular those associated with consumer behavior, have the potential to greatly reduce emissions. Therefore, strategies to influence consumer behavior should be explored.

Livestock agriculture is a source of methane (CH4), nitrous oxide (N2O) and ammonia (NH3) emissions. A comprehensive approach aimed at mitigating these emissions is needed to reduce the environmental footprint of agriculture. This thesis examined three aspects of a comprehensive mitigation strategy which included: evaluating a management consideration, improving flux measurement techniques, and modeling emissions. The relationships between total solids (TS), gas emissions and surface crust dynamics were assessed. Diurnal and long–term CH4 and N2O flux variations were examined in the context of improving discrete sampling protocols. Finally, a mechanistic model that predicts CH4 emissions from manure slurries was evaluated. Over long–term storage, the crusts were not effective in mitigating total gas emissions because the slurries remained open to the atmosphere for a significant portion of the time. Total CH4 and NH3 emissions were related linearly to TS, while N2O exhibited a sigmoid response. The linear response to TS observed for CH4 and NH3 occurred despite varying crust conditions suggesting that the availability of substrates in slurries is the more important regulator of emissions over long–term storage. Diurnal CH4 and N2O flux variations were linked with the diurnal surface temperature (T0) cycle, with the strength of the relationship depending on surface crust conditions. An assessment of discrete sampling protocols revealed that sampling intervals should be ≤7 d. In terms of the timing, it is best to sample these gases when the T0 is closest to the daily mean, which would typically be before 0900 h or after 1700 h. A mechanistic model of CH4 emissions from slurries was evaluated. The model was most accurate during the first 47 d of storage, after which the accuracy decreased. However, total emissions estimated over 145 d were within –21.1 to 6.0% of measured emissions for slurries with TS 3.2%, 5.8% and 8.2%. Emissions were also modeled using the USEPA inventory method. There was relatively good agreement between the USEPA and mechanistic models, with relative percent differences ranging from 19.9 to 37.3%, which is encouraging from the standpoint of advancing greenhouse gas inventory methods. / Ontario Graduate Scholarship